Haters gonna hate, but Monte Cook’s old Arcana Unearthed was the first thing that leap to mind for me. Heck, the trade dress of everything he did under Malhavoc was gorgeous. Clean, airy, impeccable typography, and lots of fantastic Sam Wood art.

Bonus: the light and airy style was a stark contrast to the ornate-border-heavy style that was prevalent in the d20 era (see Mongoose for some of the worst abuses of this trend), and so it totally pissed off lots of gamers because, duh, blank white space is essentially robbery, because it’s all about the ink-to-page ratio. Remember, RPGs are basically bulk produce, right?